Interfacial Engineering to Advance Anisotropic Thermoelectric Properties of Bi2Se0.3Te2.7·MoSe2 Composites

Interfacial engineering acts an effective route to decouple electronic and phonon transport in Bi2Te3-based thermoelectric materials. In this work, Bi2Se0.3Te2.7 (BST) + x wt % MoSe2 (x = 0, 1, 2, 4) composites were prepared by hot-pressing mixtures of BST and MoSe2 to construct composites with electronically active BST·MoSe2 heterointerfaces. Carrier concentration and mobility increased after MoSe2 incorporation. At the same time, ultraviolet photoelectron spectroscopy (UPS) revealed Fermi-level modulation and a reduction in work function following MoSe2 incorporation, consistent with interfacial electronic interactions. Although the electronic thermal conductivity increases with increasing MoSe2 content, the total thermal conductivity decreased from 0.99 to 0.77 W m–1 K–1 at 300 K for BST + 4 wt % MoSe2, demonstrating the effective suppression of phonon-mediated heat transport. This finding reveals selective electron–phonon transport decoupling, in which BST·MoSe2 interfaces enhance carrier transport while scattering phonons through interfacial disorder and other factors. The average zT in the temperature range of 300–500 K is determined to be 0.84 for the BST + 4 wt % MoSe2 composite, a noticeable improvement to that of BST (0.71), along with an increased hardness. This work highlights MoSe2 as a promising secondary phase for electronic modulation, phonon scattering, and improved mechanical properties in Bi2Te3-based thermoelectric materials.